The present invention relates generally to accessory mounts for firearms. More particularly, the present invention relates to accessory mounts for rifles and carbines.
It is common in the field of firearm design for accessories to be made available as an after market solution to common needs or desires not satisfied by a standard rifle or carbine. In the interest of compatibility a standardised connector rail has been developed that is a series of ridges and recesses with perpendicular sides and bases. Accessories such as laser and infra-red sights have been developed as a supplement to the optical sight that is commonly attached to the barrel of the rifle. These sights are offered as after market solutions for individuals seeking more versatile or accurate targeting methods. Other accessories such as bipods and stands are also available, as are more specialised devices that are designed as accompaniments to assault rifles. For a sight to be functional, it must be mounted so that it is coaxial with the barrel of the firearm. This allows the alignment of the sight to be maintained as the user of the firearm tracks a target.
The common method of attaching these accessories mounts is to attach one end of the accessory mounting rail to the stock of the rifle. This style of accessory rail typically mounts atop the handguard attached to the barrel of the rifle, and is additionally connected to the shoulder support that forms the butt of the weapon. These rails provide the user of the weapon with the ability to attach one or more accessories. It is known in the art that these rails can support attachments on more than one side of the weapon. This method of attaching to the stock of the rifle is unable to maintain a coaxial alignment with the barrel of the rifle, as the disassembly of a firearm for cleaning necessitates the removal of the handguard, which upon reattachment can introduce misalignment. Additionally, the stock of the rifle and the handguard are separate elements, and can be jarred from alignment during the discharging of the firearm, or through the handling of the weapon. Slight angular movement of the rail with respect to the barrel, which can be introduced through the shifting of the handguard or the stock, results in inaccuracy of the firearm system, as the accessory rail ballistic sight path will no longer correspond to the trajectory of the bullet launched from the barrel.
One notable accesory mount is described In U.S. Pat. No. 5,826,363 to Olson. This patent teaches the replacement of the handguard by a handguard with an Integral accessory rail. The accessory mount taught by Olson attaches directly to the barrel of the firearm, and secures to the stock, and the gas block.
During the use of the firearm, the barrel is heated by the combustion of the propellant in each round of firearm ammunition. This heating can cause heat based deformation of the accessory rail. Typically firearms are air-cooled, and the exterior surface of the barrel has been shown to achieve surface temperatures on the order of 300xc2x0 C. depending on the rate of fire, number of rounds fired, and the exterior configuration of the barrel. In use, the barrel will be subject to rapid eating, and a slower cooling process, where the barrel will continue to increase to a maximum temperature after the rounds have been fired. In many conventional firearms, heating related problems are mitigated through mounting the accessory rail on the handguard which dissipates the heat, but results in a higher mounting point for the accessories. In serving as both the handguard and accessory rail, the devices taught by the Olson reference employ a leaf spring and rear clamp arrangement that attempts to compensate for thermal distortion and the mechanical forces exerted by firing ammunition, both of which contribute to misalignment of the rail. An accessory rail, as taught by the Olson reference, is located on the region of the barrel that is subject to greatest heating. Accessory alignment is affected by the the thermal expansion of the handguard/accessory rail, and the movement of linkages and attachment points resulting from the thermal expansion. Though the use of the leaf spring and rear clamp arrangement taught by Olson overcomes some of the problems caused by heat dissipation, the leaf spring and clamp increase the mass of the weapon, and result in a more complex weapon design, which is undesirable for reasons of cost, maintenance and reliability. The accessory rail of the Olson reference uses the leaf spring and rear clamp to affix the handguard accessory rail to the barrel of the rifle, and to maintain a coaxial alignment of the rail to the barrel. However, while in use with a bipod accessory stand attached to the rail, the rifle is subject to short an intermittent periods of force which result from the recoil associated with the discharge of a round of ammunition, these forces can cause coaxil misalignment of the one or more accessory mounting rails.
It is, therefore, desirable to provide an accessory rail for mounting on a firearm that reduces the potential for parallax error, while avoiding the use of complex and expensive mounting arrangements to allow for heat dissipation and compensate for thermal distortion.
It is an object of the present invention to obviate or mitigate at least one disadvantage of previous firearm accessory rails.
In a first embodiment of the present invention, there is provided a firearm accessory mounting rail for attachment of a firearm accessory to the barrel of a firearm having a sight attached to the barrel. The accessory mounting rail comprises an accessory rail and a mounting bracket. The accessory rail is for providing a connection for the firearm accessory. The mounting bracket is provided on the accessory rail to allow attachment of the accessory rail to the barrel of the firearm and for engaging the sight to impede movement of the accessory rail with relation to the barrel of the firearm in at least one direction. In an embodiment of the present invention the accessory rail is integrally formed with the mounting bracket, and the mounting bracket is sized for attachment to the barrel under the sight. In an alternate embodiment of the present invention, the mounting bracket is sized to abut the sight to impede movement of the accessory rail in line with the axis of the barrel. In another embodiment of the present invention, the mounting bracket is formed of two complementary sides, each side having a complementary recess that in combination define an aperture through which the barrel can be secured. In a further embodiment, each complementary side has an integrally formed accessory rail and complementary sides are pivotally hinged to each other at their bases, where they interlace to form an accessory rail. In another embodiment, firearm accessory mounting rail is securable to the barrel through the attachment of the complementary sides to each other, with a fastener. In a further embodiment, the recesses define an aperture sized to secure the mounting bracket to the barrel and at least a portion of the sight, to impede rotation of the accessory rail with respect to the axis of the barrel.
In an embodiment of the present invention the accessory sight is secured to the barrel at the gas block to reduce the potential for thermal distortion, and to allow a connection to both the barrel of the rifle and the sight that will allow for maintenance of the coaxial alignment of the accessory rail and the barrel.
The present invention makes the accessory rail mount coaxial and solid to the barrel, thereby providing a stable sight platform, for lasers and other sights, that is capable of moving with the barrel. By being located directly on the barrel at the gas block, which is contained within the front sight, the accessory mounting rail is not exposed to the same degree of thermal distortion, as the heat is less than if the accessory mounting rail had been mounted to the barrel in the region of the handguard. This minimises the heat input to the accessory rail and thereby minimises deformation. The accessory mounting rail of the present invention serves as a heat sink for the gas block to aid in the dissipation of heat from the cooler region of the barrel without causing misalignment of the accessory mounts due to thermal distortion. The accessory mounting rail does not substantially increase the mass of the firearm system, and thus does not detrimentally affect the firearm dynamics, nor is it a great inconvenience to the user. The accessory mounting rail also provides, in a presently preferred embodiment, a means for rapidly attaching and detaching from the barrel of the rifle.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.